1. Field of the Invention
Methods and apparatuses consistent with the present invention relate to generating a stereoscopic image format and reconstructing stereoscopic images, and more particularly, to generating a stereoscopic image format on a block basis in order to efficiently compress or transmit stereoscopic images composed of a base view image and an additional view image, and reconstructing the stereoscopic images from the block-based stereoscopic image format.
2. Description of the Related Art
Many methods have been proposed to transmit stereoscopic images. For example, for efficient transmission of stereoscopic images, standards such as Moving Picture Experts Group (MPEG)-2 Multiview Video Profile (MVP), depth map transmission using MPEG-4 Multiple Auxiliary Component (MAC), Multiview Video Coding (MVC) of MPEG-4 Advanced Video Coding (AVC)/H.264, and the like have been established.
However, those standard formats are not compatible with existing two-dimensional (2D) codecs. As a result, when stereoscopic images are transmitted using the standard formats, users of related art 2D reproduction devices cannot reconstruct the stereoscopic images by decoding received data. Moreover, many problems are anticipated in transmitting three-dimensional (3D) images using the standard formats under existing channel capacity conditions.
Thus, techniques for transmitting stereoscopic images after combining the stereoscopic images into one sheet of a combined image format have been developed. A side-by-side scheme and a top-bottom scheme are representative examples of these techniques. The former reduces the number of horizontal pixels of each of a left view image and a right view image by ½ and disposes the reduced left view image and the reduced right view image in a left and right portion of one sheet of a combined image, respectively. The latter reduces the number of vertical pixels of each of the left view image and the right view image by ½ and disposes the reduced left view image and the reduced right view image in a top and bottom portion of one sheet of a combined image, respectively.
However, combined images transmitted using these schemes have resolutions that are ½ those of the original left and right view images during the reduction process. Consequently, a related art 2D reproduction device shows only half of each of the left and right images, which may be displeasing for a viewer. Moreover, correlation between a left view image and a right view image of stereoscopic images is not considered during compression or transmission of a combined image, causing degradation in compression efficiency.
One sheet of an image format may also be generated by combining a left view image and a right view image on a pixel basis.
FIG. 1A illustrates a related art pixel-based stereoscopic image format for transmission of stereoscopic images.
In FIG. 1A, pixels of a left view image and a right view image of stereoscopic images are sampled on a lattice basis and the left view image is moved by one pixel in such a way that overlap between the left view image and the right view image is avoided, thereby generating one sheet of an image format for the stereoscopic images. The stereoscopic images are transmitted and received using related art 2D encoder and decoder. Since two sheets of the left view image and the right view image are generated into one sheet of a stereoscopic image format of the same resolution, some pixels may be lost.
FIG. 1B is a block diagram of an apparatus for restoring lost pixels of a pixel-based stereoscopic image format.
In order for a display device to reproduce an image with the original resolution, pixels that are lost during generation of the stereoscopic image format illustrated in FIG. 1A have to be restored. To this end, pixel values for each direction are extracted from images sampled on a pixel basis, a predetermined weight value is applied to each of the pixel values, and the weighted pixel values are summed up, thereby reconstructing the original left and right view images.
For transmission of stereoscopic images, an image format may be generated on a field basis.
FIG. 2A illustrates a related art field-based stereoscopic image format. In FIG. 2A, an input left view image and right view image are disposed in a vertical direction line by line and are then converted to a field-based format (including a top field and a bottom field for transmission and reception.
FIG. 2B is a block diagram of a related art transmission end and a reception end for a field-based stereoscopic image format.
Referring to FIG. 2B, a stereoscopic image pre-processor for generating and encoding a stereoscopic image format and a stereoscopic image post-processor for decoding a received stereoscopic image format to reconstruct stereoscopic images are illustrated. A left view image and a right view image converted to a field-based format are compressed by an MPEG encoder. Since MPEG standards other than MPEG-1 support field-based compression, the MPEG standards maintain compression efficiency during block-based Discrete Cosine Transformation (DCT), motion estimation, and disparity estimation.
In the pixel-based stereoscopic image format illustrated in FIG. 1A, a left view image and a right view image are combined on a pixel basis in order to generate one sheet of an image format. As a result, the performance of a DCT coder according to video standards, such as Joint Photographic Experts Group (JPEG), MPEG, H.26X, and the like, and compression efficiency degrade due to low correlation between pixels. Moreover, related art image formats including the formats illustrated in FIGS. 1A and 2A are not defined for a stereoscopic image pre-processor or a stereoscopic image post-processor. As a result, a left view image and a right view image are displayed one after another on a field basis when a stereoscopic image format is decoded, causing a viewer to experience a serious flickering effect.